1. Field of the Invention
The present invention is broadly concerned with a lateral soil compaction auger designed for use in the formation of bore holes without generating undue amounts of spoil. The preferred auger includes, along the lower extent thereof, strategically spaced compaction rollers mounted within the auger shaft and operable to laterally displace and compact soil during bore hole formation. The preferred auger also includes a lower end cap mounted for rotation with the auger but having retention structure assuring that the cap is not lost during withdrawal of the auger from the bore hole. Additionally, the preferred auger assembly of the invention is equipped with control apparatus such as cementious material (e.g., grout or cement) pressure and flow monitoring and adjusting structure, and drill depth sensing means allowing the user to precisely control formation of bore holes and filling thereof. The augers of the invention may advantageously be equipped with an elongated drilling extension section below the lateral compaction portion thereof, allowing the augers to drill into high density soils below a softer area subject to lateral compaction.
2. Description of the Prior Art
Structural piles are commonly formed through the use of auger pressure grouting techniques. In such operations, an upright support cage or frame is positioned adjacent a pile site and an auger assembly is mounted to the frame including an elongated, flighted auger having a hollow central shaft. During pile-forming operations, the auger is shifted downwardly and rotated so as to screw into the earth. When the auger reaches a desired depth, it is withdrawn and grout or other cementious material is directed under pressure through the central auger shaft to create the pile. These conventional operations create substantial amounts of "spoil", meaning the displaced earth created by the auger and conveyed upwardly to grade. This spoil must be removed and this represents a considerable expense.
Soil displacement augers have been proposed in the past which substantially reduce or eliminate the spoil problem. In such augers, the shaft and flighting is designed so as to laterally displace the soil during bore hole formation and to compact the soil at the periphery of the bore hole. Most lateral displacement augers employ an expanding spiral configuration to displace and compact the earth. This expanding spiral configuration generates great friction, requiring high torque drilling rigs with pull-down capabilities up to 12,000 pounds. Even with high torque and pull-down capabilities, drilling depth with conventional lateral soil displacement augers is greatly reduced.
It also occurs during pile formation that undue pressure is developed as an adjunct to filling. If such pressures are generated, the cementious material can be caused to rapidly set, thus effectively entrapping the auger bit and causing its loss. This of course represents a very significant expense to the construction company, and is to be avoided at all costs.